1. Field of the Invention
This device pertains to safety and arming devices for fuzes used in warheads. In particular, it pertains to safety and arming devices requiring dual mode initiation, such as mechanical-electrical conditions, prior to the safety devices being removed for detonation. In even greater particularity, the present invention pertains to devices using a mechanical timer which is not prone to change its timing due to lateral forces acting on the timing device.
2. Description of the Prior Art
U.S. Pat. No. 3,498,225 to Voida et al. is a patent for a counter-rotating dual rotor safety and arming mechanism. The Voida et al. patent provides counter rotating weights to offset the influence of lateral acceleration forces encountered due to motion of a missile. Such motion is due to steering and buffeting of the missile as it moves through the atmosphere. The Voida et al. patent uses a linear arrangement of rotors and setback weight to provide a single action firing device. A pair of coil compression return springs are mounted in the Voida et al. patent so that it can function as a fly forward device.
U.S. Pat. No. 3,554,128 to Hoelzen is for a method of modifying the device taught in the Voida et al. patent so that it can be tested and reset without destroying the integrity of the safety-arming device. The Hoelzen patent is an improvement of the Voida et al. device. As such, it contains some of the limitations of the Voida et al. device. These include the need to turn the device in a preferred direction to reset everything along a singular linear axis, that the safety-arming device has to comprise a main body element covered with a top plate and a bottom plate, and the use of coil compression return springs for guiding the longitudinal motion of a set back weight.
The device taught in the Voida et al. and Hoelzen patents does not improve reliability to any significant degree. The in-line arrangement of rotors is still subject to timing shifts despite the counter balancing and control timing by an escapement device. It has also been found that the Voida et al. device requires an acceleration above one g for the device to successfully function. As a result, firing efficiency places a premium on missiles obtaining a predetermined cut off acceleration. The balancing of the rotors in the Voida device is a critical consideration and slight imbalance in the cast rotors prevents the device from working in the idealized fashion described. Lastly, the in-line arrangement requires an in-line firing train. This firing train fails if any component along the line fails. Even with an improved shelf life, the pyro-technical device used as an explosive lead could still fail resulting in total failure of the system.